Between 550,000 and 1.4 million people in West Africa could be infected with the Ebola virus by January 20, 2015, according to a report issued on Tuesday by the U.S. Centers for Disease Control and Prevention (CDC).

The top range of the estimate, 1.4 million, assumes that the number of cases officially cited so far, 5,864 according to the count kept by the World Health Organization, is significantly underreported, and that it is likely that 2.5 times as many cases, or nearly 20,000, have in fact occurred.

CDC emphasized that the projections, based on an epidemiological model that takes into account how many people each Ebola patient eventually infects as well as other factors, is based on data available in August. They therefore do not account for the recently announced U.S. government Ebola relief effort, which includes sending 3,000 members of the armed forces to the Ebola-stricken region.

"Extensive, immediate actions - such as those already started - can bring the epidemic to a tipping point to start a rapid decline in cases," CDC said in a statement.

The agency's best-case model projects that by getting 70 percent of patients into facilities where the risk for transmission is reduced and burying the dead safely, the epidemic would be "almost ended" by January 20.

Liberia in peril

A senior U.N. official warned the escalating Ebola crisis in Liberia is threatening the social fabric of the country, reversing many of the social, economic and political gains achieved since Liberia emerged from civil war.

U.N. special representative Antonio Vigilante said Tuesday the number of Ebola cases in Liberia is doubling every few weeks and stands at more than 3,000. About half of those infected have died.

“While in the last [few] years Liberia was growing at a very interesting rate, the projections for this year have already been slashed by half and perhaps now 70 percent," Vigilante said.

"Production in the mining industry and the agricultural sector and the forestry sector are slowing down, and many in the concessions are actually closed or have had their activities reduced significantly."

Vigilante said poverty is increasing as people lose their livelihoods, markets are short of supplies and people are going hungry because food prices are soaring.

Experimental drug trials

Meanwhile, it was revealed that experimential Ebola drugs will be tested in West Africa for the first time, as part of an initiative to quickly find treatments for the vicious disease.

A London-based charity, the Wellcome Trust, said Tuesday it is giving $5.2 million so a consortium of aid groups, research institutions and the World Health Organization can set up clinical trials at Ebola treatment centers.

There is currently no cure or vaccine for Ebola, which has infected more than 5,600 people and killed more than 2,800 in West Africa this year, mostly in Guinea, Liberia and Sierra Leone.

The Wellcome Trust says drugmakers taking part in the project include Mapp Biopharmaceutical, whose untested Zmapp drug has been given to a small number of Ebola patients, as well as a Canadian company, Tekmira, and U.S.-based Sarepta.

Precise details of how the trials will be carried out are still under discussion. The Wellcome Trust says participating groups are working with health officials in the affected countries to choose the best sites for the trials.

WHO says the number of people infected with Ebola could grow at an "explosive" rate - exceeding 20,000 by November - unless more is done quickly to control the outbreak.

The New England Journal of Medicine published a report Tuesday by WHO's Ebola Response Team warning that efforts to isolate patients, increase clinical care, safely bury bodies and engage the community must improve quickly to avoid a sharp increase in cases.

WHO Strategy Director Christopher Dye, a co-author of the report, says it is important to act now.

"One of the key messages that we want to get across is that we are now in the third explosive phase of growth of the epidemic," he said. "This is an exponential increase with hundreds, going into thousands of cases per week, and if we don't stop the epidemic very soon, this is going to turn from a disaster into a catastrophe."

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The report comes six months after the WHO was first notified of the Ebola outbreak. The virus has infected 5,864 people and killed 2,811.

Tuesday's report says that although Ebola has been reported in many parts of Guinea, Liberia and Sierra Leone, more than 90 percent of the cases have been in just 14 of 67 total districts in those countries.

WHO said Monday that the outbreak appears to have been stopped in Nigeria and Senegal, with no new cases in Nigeria since September 8 and none in Senegal since its first and only case was reported on August 29.

Another 30 to 40 U.S. military personnel are due to arrive in West Africa on Tuesday, joining 60 Americans already there, as part of the U.S. effort to combat Ebola. The United States has committed $175 million to help combat the outbreak and is sending 3,000 troops to the region to build field hospitals and provide logistical aid.

WHO has called for an end to flight cancellations and travel restrictions to the Ebola zone. It says these measures hamper international relief efforts and hurt the countries' economies.Lisa Schlein in Geneva contributed to this report. Some material was provided by Reuters